This invention is adapted to be embodied in a primarily manually operated vehicle with a power assist and more particularly to an electrically power assisted vehicle of this type.
There has been proposed a type of vehicle that is designed to be operated primarily by the manual force of the operator or rider. However, in order to permit individuals who may have some physical disabilities or persons of lessor strength to enjoy the exercise of such vehicles, it has been proposed to provide an electric power assist for the operation of these vehicles. In addition to permitting such disadvantaged persons to utilize such vehicles, the use of the power assist permits people having normal or greater than normal abilities also to utilize the vehicle to a fuller advantage.
The electric power assist is provided by an electric motor that is powered periodically from an electric battery in response to certain control conditions so as to provide the desired power assist. Obviously, this type of vehicle is quite small and compact and, accordingly, the size of the batteries which are carried by the vehicle are limited. It is also desirable to employ batteries that are rechargeable for a wide variety of purposes.
It is known that when rechargeable batteries are employed, it is desirable to prevent total depletion of the power of the battery before it is recharged. This prevents permanent damage and/or shortened life span of the battery. Therefore, the control systems normally include a mechanism which requires the operator to charge the battery before it is fully depleted. One way in which this charging may be called for is by having the electrical circuit discontinue the supply of electric power once the battery voltage falls below a predetermined value.
However, it is also well known that most rechargeable batteries have a so called "memory". Thus, if the battery is recharged before it is depleted to a certain relatively low value but still above the value where damage may occur, then the life of the battery will gradually deteriorate. However, this memory effect becomes cumulative and results in a vicious cycle wherein the batteries must be charged more and more frequently and eventually become relatively useless because their life is so foreshortened.
There have been proposed, therefore, systems that provide an arrangement wherein the charging of the battery is not required until the voltage falls below a value which is varied in relation to certain functions. That is, a constant predetermined voltage is not set for determining the necessity for recharging. Rather, the voltage at which recharging is required is set in accordance with a variable condition.
With this type of vehicle, however, the manual power is frequently applied through a pedal mechanism. The pedal mechanism itself, because of the varying effective ratios of the crank arms, causes the operator demand to appear to vary even though the pedaling effort may be constant. Hence, even if such variable voltage levels are set, it is relatively easy to exceed them and cause the system to disable the battery and require its charging. Thus, the problem aforenoted continues to exist.
In addition to this problem, the variable voltage threshold concept can raise further problems which along with its complexity make it also undesirable to utilize in some instances. That is, when the voltage at which charging is required is varied at one or more predetermined levels, the area between those levels is constant at the lowermost value and thus the systems do not really fully perform their intended function.
It is, therefore, a principle object of this invention to provide an improved power-assisted manually power vehicle.
It is a further object of this invention to provide a battery controlled system for power assisted, manually operated vehicles wherein the recharging life of the battery may be maintained relatively constant and the battery life and recharging times extended.
It is a further object of this invention to provide an arrangement for an electric power assisted vehicle wherein the time at which the battery must be recharged is geared more closely to the actual battery condition than with certain prior art types of devices.
As has been noted, many of the types of control system employed have in essence disabled the battery from further utilization when its voltage falls below a predetermined value. Due to the very nature of the persons which are encouraged to use this type of vehicle, however, this can be undesirable. That is, if the battery condition falls below a predetermined value when the user is at a long distance from his home or a place where recharging is possible and the battery power is shut off, the individual may not be able to pedal the vehicle back to the place where it can be charged.
It is, therefore, a still further object of this invention to provide an improved battery power-assisted vehicle wherein the operator is given adequate warning of low battery level and the battery assist is not discontinued immediately so that the operator may utilize battery power assist to return to a source where the battery can be charged.